JPH0976781A - Four-wheel drive vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a four-wheel drive vehicle capable of controlling noises and vibration in a car floor caused by the generation of hydraulic fluid pulsating pressure during traveling on a high friction coefficient road which requires no driving forces from a drive wheel shaft to a follower wheel shaft, reducing fuel consumption and suppressing the temperature increase of the hydraulic fluid. SOLUTION: The hydraulic fluid of a flow rate is discharged from a fluid pressure pump 6 by the rotation of a drive wheel shaft 4 driven by a main prime mover 1 according to a rotational speed and this fluid is supplied through a first flow passage 8H to a fluid pressure pump motor 10 as a fluid pressure driving means. When a rotational speed difference between a drive wheel shaft and a follower wheel shaft is smaller than a reference rotational speed difference ΔNF, a control means 24 controls a solenoid switch valve 22 to switch to a first position. At this time, since the delivery and suction port sides 6c and 6b of the fluid pressure pump 6 are communicated with each other, a hydraulic fluid discharged from the delivery port 6c of the fluid pressure pump 6 is prevented from flowing to the first flow passage 8H and instead, the fluid is supplied through a bypass flow passage 20 and the solenoid switch valve 22 to the suction port 6b side of the fluid pressure pump 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a four-wheel drive vehicle in which a rotational driving force of a main engine is transmitted to front wheels and rear wheels, and more particularly to a four-wheel drive vehicle in which the driving force is transmitted by working fluid pressure. It relates to a wheel drive vehicle.

[0002]

2. Description of the Related Art In a four-wheel drive vehicle of this type, in the case of a four-wheel drive vehicle in which the mechanical connection between two-wheel drive and four-wheel drive is manually switched like a part-time system, the switching operation is Besides being troublesome, it is not suitable for passenger cars due to problems such as tight corner braking. On the other hand, a full-time four-wheel drive vehicle can eliminate the tight corner braking phenomenon, but it requires a differential limiting device for the center differential, which complicates the device. Further, regardless of the part-time type and the full-time type, since the drive system used in the current passenger cars has a propeller shaft, this increases the weight of the front-wheel drive vehicle, adversely affects the vehicle interior space, and deteriorates fuel efficiency. Noise and vibration are worsened, and even in the case of a rear-wheel drive vehicle, there is an unavoidable increase in weight and fuel consumption.

[0003] Therefore, conventionally, for the purpose of reducing the weight of the constituent members, for example, JP-A-3-224830 (hereinafter, referred to as
Power transmission of a four-wheel drive vehicle having front wheels that are directly driven by a prime mover and rear wheels that are driven via a clutch operated by fluid pressure, as described in the first conventional example). A device, which is driven in association with the front wheels
A fluid pressure pump, a second fluid pressure pump that is driven in conjunction with the rear wheel, and a connecting oil passage that connects the discharge port of the first fluid pressure pump and the suction port of the second fluid pressure pump. A first fluid pressure pump and a first fluid pressure pump due to a difference in rotation speed between the front wheel side and the rear wheel side, and a hydraulic pressure supply oil passage that connects and connects the connecting oil passage and the working hydraulic chamber of the fluid pressure clutch. A four-wheel drive vehicle has been proposed in which the transmission of driving force is controlled by controlling a clutch according to the flow rate difference between two fluid pressure pumps.

Further, instead of the propeller shaft, a hydraulic transmission is used to transmit the driving force from the drive axle to the driven axle only when the main drive wheels slip on a low friction coefficient road or the like. As described in Japanese Patent Laid-Open No. 1-223030 (hereinafter, referred to as a second conventional example), a first hydraulic pump configured by, for example, a vane pump, which rotates in conjunction with a drive axle and generates hydraulic pressure according to a rotation speed. And a second hydraulic pump that is also composed of a vane pump that rotates in conjunction with the driven axle and generates hydraulic pressure according to the rotational speed,
There has been proposed one having a configuration including an oil passage that connects one of the discharge ports of the first and second hydraulic pumps and the other of the suction ports, respectively.

However, in the four-wheel drive vehicle of the first conventional example described above, the propeller shaft can be made lighter by limiting the transmission torque, but the propeller shaft cannot be omitted. However, there is an unsolved problem in that there is a certain limit to the realization and that no improvement can be made against the adverse effect on the vehicle interior space. In addition, in the four-wheel drive vehicle of the second conventional example, since the hydraulic transmission is used, the propeller shaft is omitted and the weight is reduced, the vehicle interior space is secured, the fuel consumption is improved, and the noise and vibration are reduced. However, since it corresponds to the reversal of the flow direction of the hydraulic fluid due to the different rotation directions of the axles during forward movement and during reverse movement, the first hydraulic pump and the second hydraulic pump can be used as a configuration.
There is no choice but to use expensive high-pressure piping for both of the pair of hydraulic pipes that communicate with the hydraulic pump of 1., and when applying hydraulic elements such as valves in the hydraulic transmission, it is necessary to handle both high and low pressures. However, there is an unsolved problem that the overall configuration becomes complicated.

[0006] Therefore, the present applicant has reduced the number of high-pressure pipes of the hydraulic transmission to simplify the overall structure and
When the rotational speed difference between the drive axle and the driven axle is small, the transmission of the driving force to the driven axle is almost eliminated to maintain the two-wheel drive state, and the transmission of the driving force to the driven axle is increased as the rotational speed difference increases. In order to maintain the four-wheel drive condition,
For example, as described in Japanese Patent Application No. 6-049146 (hereinafter, referred to as a third conventional example), a drive axle driven by a main prime mover and the drive axle rotate in conjunction with the drive axle.
It is composed of, for example, a fluid pressure pump configured by, for example, a suction throttle type piston pump that discharges a working fluid in a fixed direction regardless of the rotation direction of a drive axle, and a swash plate type variable displacement pump motor that rotates in conjunction with a driven axle. Fluid pressure pump motor and, for example, 2 connected to the fluid pressure pump motor
A forward / reverse switching means composed of a 4-port electromagnetic directional switching valve, a high-pressure flow passage communicating the discharge port of the fluid pressure pump with a suction port of the forward / reverse switching means, and a discharge of the forward / reverse switching means. A low-pressure flow path that communicates the outlet with the suction port of the fluid pressure pump; a torque limiting means that defines an upper limit of the transmission torque between the fluid pressure pump and the forward-reverse switching means; It has been proposed to have a configuration including a check valve that allows a fluid flow from the low pressure passage to the high pressure passage side, which is inserted in a communication passage that connects the high pressure passage and the low pressure passage.

[0007]

However, in the four-wheel drive vehicle of the third conventional example described above, the working fluid is the fluid pressure pump even during normal traveling in which a driving force from the drive axle to the driven axle is not required. Circulates to the fluid pressure pump motor from the high pressure passage through the high pressure passage, and the pulsating pressure due to the pulsation of the flow rate of the working fluid vibrates the pipe of the high pressure passage arranged under the floor in the vehicle.
It is more disadvantageous than FF vehicles in terms of noise and vibration to the floor inside the vehicle. Further, when the vehicle normally travels, the working fluid circulates in a pipe having a long high-pressure flow path, which easily causes pressure loss, which is disadvantageous in terms of fuel consumption and temperature rise of the working fluid.

Further, for example, the transmission is a manual transmission,
When the vehicle is moved backward by performing the clutch disengagement operation of the manual transmission in the middle of an uphill, if the flow path of the forward / reverse switching means linked to the shift is not switched, the operation is discharged from the fluid pressure pump. It is expected that the fluid will be contained in the high pressure flow path. At this time, the working fluid is confined in the high-pressure flow path, so that a braking torque is generated according to the cracking pressure of the relief valve, which may give the driver a feeling of strangeness.

Therefore, the present invention has been made by paying attention to the unsolved problem of the above-mentioned conventional example, and the working fluid is used when traveling on a high friction coefficient road that does not require a driving force from the drive axle to the driven axle. It suppresses noise and vibration to the floor inside the vehicle due to the generation of pulse pressure, improves fuel efficiency and suppresses temperature rise of working fluid, and eliminates driver discomfort because braking torque is not generated during forward / reverse switching. It is an object of the present invention to provide a four-wheel drive vehicle that is capable of driving.

[0010]

In order to achieve the above-mentioned object, the invention of claim 1 is a drive axle driven by a main engine, and a fluid which rotates in conjunction with the drive axle and discharges a working fluid. A fluid pressure supply means having a pressure pump, a fluid pressure drive means having a fluid pressure pump motor that rotates in conjunction with a driven axle, a discharge port of the fluid pressure pump and a suction port of the fluid pressure drive means. A four-wheel drive vehicle including a first flow path and a second flow path that communicates the discharge port of the fluid pressure drive means with the suction port of the fluid pressure pump. A bypass flow passage communicating with the mouth side; a first position inserted in the bypass flow passage to bring the discharge port and the suction port of the fluid pressure pump into communication with each other; and the discharge port and the suction port of the fluid pressure pump. The electric power that switches to the second position that is in the non-communication state. A switching valve, a rotational speed difference detecting means for detecting a rotational speed difference between the drive axle and the driven axle, and control for switching control of the electromagnetic switching valve based on the rotational speed difference detected by the rotational speed difference detecting means. The control means presets a value having a small rotational speed difference between the drive axle and the driven axle generated in the two-wheel drive traveling state as a reference rotational speed difference, and the rotational speed by the rotational speed difference detecting means. When the detected value of the difference is less than or equal to the reference rotational speed difference, the electromagnetic switching valve is switched to the first position, and when the detected value of the rotational speed difference exceeds the reference rotational speed difference, the electromagnetic switching valve is turned on. It is arranged to switch to the second position.

According to a second aspect of the present invention, there is provided a drive axle driven by the main prime mover, a fluid pressure supply means having a fluid pressure pump that rotates in conjunction with the drive axle and discharges a working fluid, and a driven body. A fluid pressure pump motor that rotates in conjunction with the axle, a forward / reverse switching valve that is disposed in the vicinity of the fluid pressure pump motor and that switches the flow path to the suction port and the discharge port of the fluid pressure pump motor, and the fluid. A high-pressure flow path that communicates the discharge port of the pressure pump with the suction port of the forward-reverse switching switching valve, and a low-pressure flow that communicates the suction port of the forward-reverse switching switching valve with the discharge port of the fluid pressure pump motor. In a four-wheel drive vehicle including a passage, a bypass flow passage that connects the discharge side and the suction side of the fluid pressure pump, and the discharge port of the fluid pressure pump and the bypass inserted through the bypass flow passage. Communication with pump suction port And a rotation speed for detecting a rotation speed difference between the drive axle and the driven axle, and an electromagnetic switching valve for switching between a first position and a second position where the discharge port and the pump suction port of the fluid pressure pump are in a non-communication state. And a control means for performing switching control of the electromagnetic switching valve based on the rotation speed difference detected by the rotation speed difference detection means, the control means comprising the drive axle generated in a two-wheel drive traveling state. And a value in which the rotational speed difference of the driven axle is small is preset as a reference rotational speed difference, and the electromagnetic switching valve is activated when the detected value of the rotational speed difference by the rotational speed difference detecting means is equal to or less than the reference rotational speed difference. In addition to switching to the first position, the electromagnetic switching valve is switched to the second position when the detected value of the rotational speed difference exceeds the reference rotational speed difference.

According to a third aspect of the present invention, there is provided a drive axle driven by a main motor, and a fluid pressure pump that rotates in conjunction with the drive axle and discharges the working fluid sucked from a working fluid supply source. A first flow communicating the fluid pressure supply means, the fluid pressure drive means having a fluid pressure pump motor that rotates in conjunction with the driven axle, and the discharge port of the fluid pressure pump and the suction port of the fluid pressure drive means. A four-wheel drive vehicle including a passage, and a second flow path that connects the discharge port of the fluid pressure drive means and the suction port of the fluid pressure pump, the supply source and the suction port of the fluid pressure pump An inlet port connected to the supply source side, an output port connected to the suction port side of the fluid pressure pump, and a part of the working fluid discharged from the discharge port of the fluid pressure pump, A control port to input as control pressure, A pilot operated type flow control valve having a throttle for limiting the flow of the dynamic fluid is inserted, and the flow control valve controls the low pressure working fluid which does not transmit the driving force to the driven axle as the control pressure. When the fluid is input to the port, it is switched to a first position that communicates the input port and the output port via the throttle, and the working fluid of a predetermined pressure that transmits the driving force to the driven axle is a control pressure. As a result, when input to the control port, the input port and the output port are switched to a second position that communicates with each other without passing through the aperture.

According to a fourth aspect of the present invention, there is provided a drive axle driven by a main motor, and a fluid pressure pump that rotates in conjunction with the drive axle and discharges the working fluid sucked from a working fluid supply source. A first flow communicating the fluid pressure supply means, the fluid pressure drive means having a fluid pressure pump motor that rotates in conjunction with the driven axle, and the discharge port of the fluid pressure pump and the suction port of the fluid pressure drive means. A four-wheel drive vehicle including a passage, and a second flow path that connects the discharge port of the fluid pressure drive means and the suction port of the fluid pressure pump, the supply source and the suction port of the fluid pressure pump An input port that is connected to the supply source side by being inserted in a suction flow path between them, an output port that is connected to the suction port side of the fluid pressure pump, and a throttle that restricts the flow of the working fluid, and Through the throttle, the input port and the output An electromagnetic flow control valve that switches between a first position communicating with the port and a second position communicating with the input port and the output port without passing through the throttle, and the rotational speeds of the drive axle and the driven axle. A rotational speed difference detecting means for detecting a difference and a control means for controlling switching of the electromagnetic flow control valve based on the rotational speed difference detected by the rotational speed difference detecting means are provided. The value in which the difference in rotation speed between the drive axle and the driven axle that occurs in a state is small is preset as a reference rotation speed difference, and the detected value of the rotation speed difference by the rotation speed difference detection means is equal to or less than the reference rotation speed difference. At this time, the electromagnetic flow control valve is switched to the first position, and when the detected value of the rotational speed difference exceeds the reference rotational speed difference, the electromagnetic flow control valve is switched to the second position.

Further, according to the invention of claim 5, there is provided a drive axle driven by the main prime mover, and a fluid pressure pump which rotates in conjunction with the drive axle and discharges the working fluid sucked from the supply source of the working fluid. A first flow communicating the fluid pressure supply means, the fluid pressure drive means having a fluid pressure pump motor that rotates in conjunction with the driven axle, and the discharge port of the fluid pressure pump and the suction port of the fluid pressure drive means. A four-wheel drive vehicle including a passage, and a second flow path that connects the discharge port of the fluid pressure drive means and the suction port of the fluid pressure pump, the supply source and the suction port of the fluid pressure pump An input port connected to the supply source side by being inserted in a suction flow path between the output port and an output port connected to the suction port side of the fluid pressure pump, and a throttle for restricting the flow of working fluid, and the throttle. Through the input port and the output From the fluid pressure supply means, and an electromagnetic flow control valve that switches between a first position that communicates with the valve and a second position that communicates the input port and the output port without passing through the throttle. A fluid pressure detecting means for detecting a change state of the pressure of the working fluid, and a control means for performing switching control of the electromagnetic flow control valve based on a detection result of the fluid pressure detecting means, wherein the control means is the fluid The electromagnetic flow control valve is switched to the first position when it is detected by the pressure detecting means that the low-pressure working fluid that does not transmit the driving force to the driven axle is reached, and the fluid pressure detecting means is used. The electromagnetic flow control valve is switched to the second position when it is detected that the working fluid having a predetermined pressure for transmitting the driving force to the driven axle has been reached.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a first embodiment when the present invention is applied to a four-wheel drive vehicle based on a front-wheel drive vehicle. Reference numeral 1 in the figure denotes an engine as a main prime mover. The rotational driving force of the engine 1 is input to a front wheel side differential device 3 via a transmission 2, and an output side of the differential device 3 serves as a drive axle. A front wheel 5 is connected via a front axle 4 of the.

In the front wheel side differential device 3, a ring gear 3b formed in a differential gear case 3a is meshed with a gear 2a connected to an output side of the transmission 2 and is rotationally driven,
A pinion 3d is attached to a pair of pinion shafts 3c formed in the differential gear case 3a, a pair of side gears 3e mesh with these pinion 3d, and a front axle 4 is connected to these side gears 3e.

Further, the differential gear case 3a
A ring gear 3f, which is formed in parallel with the ring gear 3b, forms a fluid pressure supply means via a gear 3g meshing with the ring gear 3f.
(Hereinafter, simply referred to as piston pump 6) rotating shaft 6a
It is connected to. The piston pump 6 includes a strainer 7 having a suction port 6 b arranged in a reservoir tank 7.
a is connected to the tank port T of the two-position four-port electromagnetic directional control valve 9 through the low-pressure pipe 8L as a low-pressure passage, and is connected to the discharge port 6 through the suction pipe 8S.
c is connected to a pump port P serving as a suction port of a forward / backward switching electromagnetic directional control valve 9 as a forward / backward switching means through a high pressure pipe 8H as a high pressure passage. Here, in the piston pump 6, the suction port and the discharge port do not interchange depending on the rotation direction of the rotating shaft 6a, and the discharge flow rate is
As shown by the characteristic curve L ₁ in FIG. 2, the rotation speed increases in proportion to the increase in the rotation speed from “0” to the predetermined value V ₁ , and the maximum discharge flow rate at the predetermined value V ₁ or higher. Q
It is set to saturate at _1MAX .

The electromagnetic directional control valve 9 for switching between forward and reverse travel is operated in the normal position where the solenoid 9a is in a non-energized state.
The pump port P serving as the suction port communicates with the output port A, and the tank port T serving as the discharge port communicates with the output port B.
Further, at the offset position where the solenoid 9a is in the energized state, the pump port P communicates with the output port B and the tank port T communicates with the output port A, and the output ports A and B are swash plate type variable displacements as a fluid pressure pump motor. Pump motor 1
0 (hereinafter abbreviated as pump motor 10) is connected to suction / discharge ports 10a and 10b, and solenoid 9
In a normal position where a is in a non-energized state, the high pressure oil in the high pressure pipe 8H is communicated with the suction / discharge port 10a of the pump motor 10, and the low pressure pipe 8L is communicated with the suction / discharge port 10b.
c is rotationally driven in the rotational direction when traveling forward, for example, clockwise as viewed from the left side surface, and conversely, the high pressure hydraulic oil in the high pressure pipe 8H is sucked and discharged from the pump motor 10 at the offset position.
Further, the low-pressure pipe 8L is connected to the suction / discharge port 10a, and the rotary shaft 10c is rotationally driven in the rotation direction during forward traveling, for example, counterclockwise when viewed from the left side surface.

The electromagnetic directional control valve 9 is built in the pump motor 10, and the suction / discharge ports 10a and 10 of the pump motor 10 are provided without the output ports A and B passing through piping.
connected to b. Further, the solenoid 9a of the electromagnetic directional control valve 9 is energized by being connected to the DC power supply 9c via a shift position detection switch 9b which is turned on when a backward movement is selected by a shift lever (not shown), whereby the vehicle travels forward. It is controlled to be in a non-energized state at times and to be in an energized state during backward traveling.

The flow rate of the pump motor 10 is a differential pressure generated at both ends of the differential pressure detecting orifice 11 inserted in the low pressure pipe 8L near the tank port T of the electromagnetic directional control valve 9 and includes the hydraulic cylinder 12a. Variable swash plate mechanism 1
By controlling the 2, as indicated by the characteristic curve L ₂ in FIG. 2, when it reaches increased in proportion to the increase of the rotational speed to the rotational speed V ₁ it was in until the rotational speed reaches V ₁ ,
The discharge flow rate Q ₂ becomes larger than the maximum discharge flow rate Q _1MAX of the piston pump 6, and thereafter, increases relatively gently as the rotation speed increases. Here, the discharge flow rate of the pump motor 10 and the discharge flow rate of the piston pump 6 are such that the discharge flow rate of the pump motor 10 is greater than the discharge flow rate of the piston pump 6 for the same wheel speed, as shown in FIG. The specific discharge flow rate and the gear ratio of the gear connected to the rotating shaft are set.

Further, as shown in FIG. 1, a relief valve 13 for defining the upper limit of the discharge pressure of the piston pump 6 as a torque limiting means is interposed in the communication pipe 14A which communicates between the high pressure pipe 8H and the low pressure pipe 8L. Each of the communication pipes 14B and 14C disposed in parallel with the communication pipe 14A has a reverse relationship in which only the fluid flow from the low pressure pipe 8L side to the high pressure pipe 8H side is allowed in parallel relationship with the relief valve 13. The stop valve 15 and the fixed orifice 16 are connected.

Further, the high pressure pipe 8H near the suction port 6b side
And a communication pipe (bypass flow path) 20 between the suction pipe 8S
Is connected to the high-pressure pipe 8H and the suction pipe 8S during normal running (when running on a high friction coefficient road).
An electromagnetic switching valve 22 that communicates with each other is inserted. The electromagnetic switching valve 22 is configured with a spring offset type two-position two-port, and has a solenoid a, an input port 22b connected to the high pressure pipe 8H on the discharge port 6c side, an output port 22c connected to the suction pipe 8S, Return spring 22
d, and a spool for switching the input port 22b and the output port 22c to a communication state or a non-communication state.
When the solenoid 22a is in the non-energized state, the spool moves to the normal position where the input port 22b and the output port 22c communicate with each other. When the solenoid 22a is energized, the spool moves to an offset position where the input port 22b and the output port 22c are not in communication. An exciting current i is supplied to the solenoid 22a from a controller 24 described later.

A gear 10d is attached to a rotary shaft 10c of the pump motor 10, and a ring gear 17b formed on a differential gear case 17a of the rear wheel side differential device 17 is meshed with the gear 10d. The rear wheel side differential device 17 has substantially the same configuration as the front wheel side differential device 3 described above, and a pair of pinion shafts 17c formed in the differential gear case 17a has pinion 1 mounted thereon.
7d is attached, a pair of side gears 17e meshes with these pinions 17d, a rear axle 18 is connected to these side gears 17e, and a rear wheel 19 is connected to this rear axle 18.

Further, the front axle 4 is provided with a front axle rotation speed sensor 26 for detecting the rotation speed thereof, and
A rear axle rotation speed sensor 28 that detects the rotation speed of the rear axle 18 is provided on the rear axle 18. The front axle rotation speed sensor 26 and the rear axle rotation speed sensor 28 correspond to the rotation speed difference detection means of the present invention, and the front axle rotation speed detection output from the front axle rotation speed sensor 26 and the rear axle rotation speed sensor 28 is detected. The value N _F and the rear axle rotation speed detection value N _R are input to the controller 24.

The controller 24 outputs and stops the exciting current i to the electromagnetic switching valve 22 based on the detection signals from the front axle rotation speed sensor 26 and the rear axle rotation speed sensor 28. That is, as shown in FIG. 3, the controller 24 includes a microcomputer 30 and a drive circuit 32 that outputs an exciting current i according to a control signal CS output from the microcomputer 30.

Then, the microcomputer 30 has an input interface circuit 30a having an A / D conversion function for reading detection signals from the front axle rotation speed sensor 26 and the rear axle rotation speed sensor 28, and electromagnetic switching according to a predetermined program. An arithmetic processing unit 30b for performing arithmetic processing for the switching operation of the valve 22 and a storage unit 3 such as a ROM or a RAM.
0c and an output interface circuit 30d that outputs the control signal CS.

Here, the storage device 30c stores in advance programs and fixed data necessary for executing the arithmetic processing of the arithmetic processing device 30b, and the processing result can be temporarily stored. Among these, as fixed data, a difference in rotational speed between the front and rear axles 4 and 18 caused when a different-diameter tire is traveling, that is, the front and rear axles 4 and 18 generated when traveling in a state where a diameter change occurs due to tire wear or the like. A reference rotational speed difference ΔN _F set to be higher than the rotational speed difference by a predetermined value is stored. When the vehicle speed increases, the rotation speed difference Δ
Since N becomes large, the reference rotational speed difference ΔN _F changes according to the vehicle speed. That is, the reference rotation speed difference ΔN _F is a function of the vehicle speed.

[0028] Then, operation in the treatment device 30b, and calculates the rear axle rotation speed detection value N the rotational speed difference ΔN that the _R obtained by subtracting (= N _F -N _R) from the front axle rotation speed detection value N _F, the rotational speed A comparison judgment is made between the difference ΔN and the reference rotational speed difference ΔN _F.
Then, the arithmetic processing unit 30b uses the current rotational speed difference Δ.
When it is determined that N is less than the reference rotation speed difference ΔN _F (ΔN <ΔN _F ), the control signal CS is not output from the output interface circuit 30d to the drive circuit 32, and the solenoid 2
Since the exciting current i is not output to 2a, the solenoid 22a
Maintains a non-energized state. On the other hand, when it is determined that the rotational speed difference ΔN is greater than or equal to the reference rotational speed difference ΔN _F (ΔN ≧ Δ
N _F ), the output interface circuit 30d to the drive circuit 3
The control signal CS is output to 2. As a result, the solenoid 22a maintains the energized state.

Next, the operation of the above embodiment will be described. now,
When the vehicle stops on a high friction coefficient road such as a dry road surface, the engine 1
When starting forward running in a braking state in which the vehicle is in the idling state, the shift lever is switched to the forward running side to enter the starting state. At this time, the shift position detection switch 9b on the reverse running side remains in the off state. Therefore, the solenoid 9a of the electromagnetic directional control valve 9 maintains the non-energized state, and the switching position continues to be the normal position shown in FIG. In this state, by releasing the brake pedal and depressing the accelerator pedal, the rotational force of the engine 1 is transmitted to the front wheel side differential device 3 via the transmission 2, and the front wheel side operating device 3 operates the front wheels 5 to operate. The forward movement is started by rotationally driving in the forward direction.

At this time, the controller 24 to which the rotation speed detection values N _F and N _R are input from the front axle rotation speed sensor 26 and the rear axle rotation speed sensor 28 is rotated by the rotation speed difference ΔN (= N _F −
N _R ) and the reference rotation speed difference ΔN _F are compared. When the vehicle travels on this high friction coefficient road, the rotational speed difference ΔN becomes almost zero, which is lower than the reference rotational speed difference ΔN _F (ΔN <ΔN _F ), so the solenoid 22a of the solenoid operated directional control valve 22.
Is maintained in the non-energized state, and the switching position is set to the normal position shown in FIG.

At this time, as the vehicle travels forward, the rotary shaft 6a of the piston pump 6 is rotationally driven clockwise as viewed from the left side surface, and the piston pump 6 discharges hydraulic fluid at a discharge flow rate according to the rotation speed from the discharge port 6c. However, since the input port 22b and the output port 22c are communicated with each other by the electromagnetic switching valve 22 which continues the normal position, most of the hydraulic oil on the discharge port 6c side passes through the electromagnetic switching valve 22 and the suction port 6b side. Will be returned to.

Therefore, the high-pressure hydraulic oil discharged from the piston pump 6 hardly flows into the pump motor 10 side from the high-pressure pipe 8H arranged under the floor in the vehicle, and the high-pressure pipe due to the arterial movement of the hydraulic oil. Since the vibration of 8H does not occur, it is possible to suppress noise and vibration to the floor inside the vehicle. Further, since the high-pressure hydraulic oil does not flow through the long high-pressure pipe 8H, the drag resistance generated by the increase in the flow rate,
That is, since the pressure loss due to the pipe resistance and the like are reduced and the occurrence of cavitation is suppressed, the deterioration of fuel consumption can be avoided. Furthermore, since the temperature rise of the hydraulic oil can be suppressed, the viscosity of the hydraulic oil can be maintained at an appropriate value.

The rear wheels 19 and the front wheels 5 as the vehicle starts moving.
The rotary shaft 10c of the pump motor 10 is rotated in the same direction at the same rotational speed as the rear wheel side differential device 17 in the clockwise direction when viewed from the left side surface. As a result, the hydraulic oil is sucked from the suction / discharge port 10a of the pump motor 10 and the hydraulic oil is discharged from the suction / discharge port 10b.
The hydraulic oil discharged from the discharge port 10b is the communication pipe 14B.
Since it passes through the check valve 15 and is returned to the suction / discharge port 10a again, the pump motor 10 does not function as a pump,
It does not affect the high-pressure pipe 8H. Moreover, the pump motor 10 does not act as a hydraulic motor, the driving force is not transmitted to the rear wheels 19, and the vehicle travels forward in the same state as the front-wheel drive vehicle.

Next, for example, when the transmission 2 employs a manual transmission, and the clutch is disengaged from the manual transmission 2 to move the vehicle backward while the vehicle is traveling uphill, the shift lever moves backward. Since it is not selected, the shift position detection switch 9b remains in the off state. As a result, the solenoid 9a is de-energized, and the switching position of the electromagnetic directional control valve 9 continues to be the normal position shown in FIG. Then, the rotary shaft 10c of the pump motor 10 rotates counterclockwise as viewed from the left side surface opposite to the forward direction, so that the working oil is sucked and
The hydraulic oil is sucked from the discharge port 10b and discharged from the suction / discharge port 10a, so that the hydraulic oil flows into the high pressure pipe 8H. However, at this time, the rotational speed difference ΔN is lower than the reference rotational speed difference ΔN _F (ΔN <ΔN _F ), so the solenoid operated directional control valve 22 continues to be in the normal position, and the hydraulic oil flows inside the high pressure pipe 8H. Is never trapped in. As described above, the present device has a structure in which the hydraulic oil is not confined in the high-pressure pipe 8H even when the clutch is disengaged from the manual transmission 2 and the vehicle is moved in the reverse direction on the way uphill. Therefore, the braking torque according to the cracking pressure of the relief valve 13 is not generated, and the driver does not feel uncomfortable. Next, when the vehicle starts on a low friction coefficient road such as an icy road or a snowy road, the front wheels 5 are first driven to rotate,
Since the road has a low friction coefficient, the front wheels 5 slip and the front wheels 5
Also, there occurs a difference in rotational speed between the rear wheel 19 and the rear wheel 19 so that the front wheel 5 has a high rotational speed.

At this time, the controller 24 determines the difference in the number of revolutions.
ΔN is the reference speed difference ΔN_FDetermined to be a value above
((ΔN ≧ ΔN_F), Solenoid 22 of electromagnetic switching valve 22
Input port 22b and output port 2 with a being energized
2c is switched to an offset position where the communication is not established. This
This cuts off the communication pipe 20.
Hydraulic oil flows from pump 6 into pump motor 10
The discharge flow rate of the pump 6 is equal to the discharge flow rate of the pump motor 10.
If it exceeds, the resistance of the pump motor 10
As a result, the working oil pressure of the high pressure pipe 8H will rise.
Therefore, the pump motor 10 operates as a hydraulic motor. This
As a result, the driving force corresponding to the pressure inside the high-pressure pipe 8H is
It is transmitted to the rear wheels 19 via the wheel side differential device 17,
Move to the active state. That is, it is transmitted to the rear wheel 19 side.
As shown in Fig. 4, the torque suddenly increases as the rotational speed difference increases.
The maximum torque is increased by the pressure limitation by the relief valve 13.
Ku T _MAXWill be regulated.

Next, when the vehicle is moved backward, the shift position detection switch 9b is turned on by switching the shift lever to the reverse position, so that the solenoid 9a of the forward-reverse switching electromagnetic directional control valve 9 is energized. Then, the switching position is switched from the normal position to the offset position.
As a result, the hydraulic oil inside the high-pressure pipe 8H is supplied to the suction / discharge port 10b of the pump motor 10, and the suction / discharge port 1
By returning the hydraulic oil discharged from 0a to the low-pressure pipe 8L side, the rotation shaft 10c of the pump motor 10 is reversed from that during forward traveling, and the rear wheel 19 is rotated in reverse.

At this time, the rotation speed difference ΔN is the reference rotation speed difference Δ.
When the value is lower than N _F (ΔN <ΔN _F ), the solenoid 22a is maintained in the non-energized state and the switching position of the electromagnetic switching valve 22 is set to the normal position, and the rotation speed difference ΔN is equal to the reference rotation speed difference ΔN _F. When it exceeds (ΔN ≧ ΔN _F ), the solenoid 22a is maintained in the energized state and the switching position of the electromagnetic switching valve 22 is set to the offset position. Therefore, when the vehicle is moving backward, the transmission of the driving force is exactly the same as when moving forward,
The pressure is generated inside the high-pressure pipe 8H only when the front wheel 5 slips and the rotational speed difference between the front and rear axles 4, 18 exceeds the reference rotational speed difference ΔN _F , and the driving force is transmitted to the rear wheel 19.

Next, a second embodiment of the present invention will be described with reference to FIG. In the second embodiment, the electromagnetic switching valve 22 inserted in the communication pipe 20 of the first embodiment is omitted, and instead, the discharge pressure of the piston pump 6 is input as the control pressure and the discharge of the piston pump 6 is input. This is a device in which a pilot-operated suction flow control valve 34 for controlling the opening of the suction passage to be small when the pressure becomes equal to or lower than the specified pressure Ps is inserted in the suction pipe 8S. It should be noted that, except that the flow control valve 34 is applied, it has the same configuration as that of the above-described first embodiment, and the portions corresponding to those in FIG. Omit it.

The flow control valve 34 is a spring offset type switching valve, and has an input port 34a connected to the reservoir tank 7 side, an output port 34b connected to the suction port 6b side of the piston pump 6, and the piston pump 6's. A control port 34c that is connected to a control pipe 35 that communicates with the discharge port 6c and is supplied with a working fluid from the control pipe 35 as a control pressure, and a return that applies a pressing force in a direction opposite to the direction in which the control pressure Ps acts. A spring 34d, an orifice 34e set to have a predetermined passage area, and an input port 34a.
And a spool for switching the output port 34b so as to communicate with each other via the orifice 34e, or the input port 34a and the output port 34b for communicating with each other without the orifice 34e.

In the flow rate control valve 34, when the control pressure supplied to the control port 34c becomes equal to or lower than the specified pressure Ps, the pressing force of the return spring 34d causes the input port 34a and the output port 34b to communicate with each other through the orifice 34e. As you do, the spool moves to the normal position. When the control pressure supplied to the control port 34c exceeds the specified pressure Ps, the spool is offset from the return spring 34d so that the input port 34a and the output port 34b communicate with each other without passing through the orifice 34e. Move to.

Here, the specified pressure Ps is high enough that the rotational speed difference between the front and rear axles 4 and 18 is substantially zero, and the pump motor 10 does not act as a hydraulic motor and the driving force is not transmitted to the rear wheels 19. It is set to a value substantially the same as the low pressure value inside the pipe 8H. The orifice 34e is formed in a narrow passage area so that a small amount of hydraulic oil flows from the reservoir tank 7 into the suction port 6b of the suction throttle piston pump. Therefore, when the flow rate control valve 34 is in the normal position, the discharge flow rate of the piston pump 6 is limited to the minimum. On the other hand, when the flow rate control valve 34 is at the offset position, the hydraulic oil in the reservoir tank 7 flows into the suction port 6b without passing through the orifice 34e, and the piston pump 6 produces the discharge flow rate shown by the characteristic curve L ₁ in FIG. Become.

According to the second embodiment having the above structure, when the vehicle travels on a high friction coefficient road, the front and rear axles 14, 18 are used.
Since there is almost no difference in the number of revolutions between them, high pressure piping 8H
The pressure of the hydraulic oil is below the specified pressure Ps. This allows
Since the flow rate control valve 34 is in the normal position and the discharge flow rate of the piston pump 6 is limited to the minimum, the high pressure pipe 8H
Almost no hydraulic oil flows into the pump motor 10 from the side. Therefore, similarly to the first embodiment, it is possible to suppress noise and vibration to the floor inside the vehicle, and it is possible to prevent deterioration of fuel consumption by reducing pressure loss due to pipe resistance and suppressing cavitation. Furthermore, the viscosity of the hydraulic oil can be maintained at an appropriate value by suppressing the temperature rise of the hydraulic oil.

When the vehicle travels on a low friction coefficient road, the front wheel 5 slips and a difference in rotational speed occurs between the front and rear wheels 5 and 19, and the discharge flow rate of the piston pump 6 becomes equal to that of the pump motor 10. Since it exceeds the discharge flow rate, pump motor 1
The resistance of 0 becomes a load and the pressure of the hydraulic oil in the high-pressure pipe 8H rises. At this time, when the pressure of the hydraulic oil in the high-pressure pipe 8H exceeds the specified pressure Ps, the control pressure supplied to the control port 34c moves the spool in a direction against the return spring 34d, and the flow control valve 34 is offset. The position. At this time, the suction throttle type piston pump 6
Is the discharge flow rate shown by the characteristic curve L ₁ in FIG. Then, since the pump motor 10 operates as a hydraulic motor, the driving force corresponding to the pressure in the high-pressure pipe 8H is transmitted to the rear wheels 19 via the rear wheel side differential device 17 to shift to the four-wheel drive state.

Next, a third embodiment of the present invention will be described with reference to FIG. In addition, also in this embodiment, the same components as those in the above-described first and second embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted. This third embodiment is the second
The flow control valve 34 used in the embodiment is omitted, and instead of this, the controller 24 controls the electromagnetic flow control valve 36 based on the rotational speed difference generated between the front and rear axles 4, 18.

The electromagnetic flow control valve 36 is a spring offset type two-position two-port electromagnetic switching valve, and is an input port 36a connected to the reservoir tank 7 side.
An output port 36b connected to the suction port 6b side of the piston pump 6, a solenoid 36c, a return spring 36d, and an orifice 3 having a predetermined passage area.
6e and the input port 36a and the output port 36b are in communication with each other through the orifice 36e, or the input port 36
a and a spool for switching the output port 36b so as to be in a communication state without passing through the orifice 36e.

The solenoid flow control valve 36 has an orifice 36e when the solenoid 36c is not energized.
The spool moves to the normal position where the input port 36a and the output port 36b communicate with each other via. When the solenoid 36c is energized, the solenoid 36c moves to an offset position where the input port 36a and the output port 36b communicate with each other without passing through the orifice 36e. In addition, the orifice 36e
Like the orifice 34e of the second embodiment described above, is formed in a narrow passage area so that a small amount of hydraulic oil flows from the reservoir tank 7 into the suction throttle piston pump.

As in the first embodiment, the controller 24 excites the solenoid 36c when the rotational speed difference ΔN between the front and rear axles 4, 18 is less than the reference rotational speed difference ΔN _F (ΔN <ΔN _F ). The current i is not output and the solenoid 36
c is maintained in a non-energized state. On the other hand, when the rotational speed difference ΔN is greater than or equal to the reference rotational speed difference ΔN _F (ΔN ≧ ΔN _F ),
The exciting current i is output to the solenoid 36c, and the solenoid 3
6c is kept energized.

According to the third embodiment having the above-mentioned structure, when the vehicle travels on the high friction coefficient road and the rotational speed difference hardly occurs between the front and rear axles 14 and 18 (ΔN <ΔN _F ), the controller 24 The solenoid 36c of the electromagnetic flow control valve 36 is maintained in the non-energized state by the control of 1) and the switching position is set to the normal position shown in FIG. As a result, the piston pump 6 limits the discharge flow rate to the minimum, so that the high pressure pipe 8H
Almost no hydraulic oil flows into the pump motor 10 side. Therefore, the same effect as the second embodiment can be obtained.

Further, the vehicle is traveling on a road having a low coefficient of friction, and the front wheels are
A slip of 5 causes a difference in the standard rotational speed between the front and rear axles 4 and 18.
ΔN_FWhen a rotational speed difference ΔN that exceeds
ΔN _F), Electromagnetic flow control by control of controller 24
Keep the solenoid 36c of the valve 36 energized and switch
The position is set to the offset position as shown in FIG. This
The piston pump 6 has a characteristic curve L shown in FIG.₁Indicated by
It becomes the discharge flow rate, and the pump motor 10 becomes a hydraulic motor.
It operates and the driving force according to the pressure of the high pressure pipe 8H is
It is transmitted to the rear wheels 19 via the driving device 17 and the four-wheel drive state
Move to.

Next, a fourth embodiment of the present invention will be described with reference to FIG. In addition, also in this embodiment, the same components as those in the third embodiment described above are designated by the same reference numerals, and detailed description thereof will be omitted. This 4th Embodiment is high pressure piping 8H.
A pressure switch 38 for detecting whether or not the pressure has reached the specified pressure Ps is provided, and the controller 24 controls the electromagnetic flow control valve 36 based on the detection value of the pressure switch 38.

Here, the prescribed pressure Ps is the same as in the second embodiment, so that the pump motor 10 does not act as a hydraulic motor and the driving force is not transmitted to the rear wheel 19.
It is set to be approximately the same as the low pressure value inside H. The pressure switch 38 outputs a detection signal S _A to the input interface circuit 30a of the controller 24 when the pressure in the high-pressure pipe 8H exceeds the specified pressure Ps. On the other hand, when the pressure in the high-pressure pipe 8H is equal to or lower than the specified pressure Ps, the input interface circuit 30
The detection signal S _A to a is stopped.

Further, the arithmetic processing unit 3 of the controller 24
0b, when the detection signal S _A is input from the pressure switch 38, the output interface circuit 30d drives the drive circuit 32
When the detection signal S _A from the pressure switch 38 is stopped, the control signal CS from the output interface circuit 30d to the drive circuit 32 is stopped.

As a result, when the vehicle travels on a high friction coefficient road, there is almost no difference in rotational speed between the front and rear axles 14 and 18, and the hydraulic oil pressure in the high-pressure pipe 8H is equal to the specified pressure Ps.
Since the pressure switch 38 is lower than
The detection signal S _A to 4 is stopped. At this time, since the exciting current i is not output from the controller 24 to the solenoid 36c, the solenoid 36c maintains the non-energized state, and the electromagnetic flow control valve 36 is in the normal position as shown in FIG.
As a result, since the discharge flow rate of the piston pump 6 is limited to the minimum, almost no hydraulic oil flows into the pump motor 10 side from the high pressure pipe 8H, and the same effect as that of the third embodiment can be obtained.

When the vehicle travels on a low friction coefficient road and the front wheels 5 slip and a difference in rotational speed occurs between the front and rear wheels 5 and 19, the hydraulic oil pressure in the high pressure pipe 8H is the specified pressure P.
s is exceeded, the pressure switch 38 outputs a detection signal S _A to the controller 24. At this time, the exciting current i is output from the controller 24 to the solenoid 36c,
Since the solenoid 36c maintains the energized state, the electromagnetic flow control valve 36 moves to the offset position. This allows
The piston pump 6 has the discharge flow rate shown by the characteristic curve L ₁ in FIG. 2, the pump motor 10 operates as a hydraulic motor, and the driving force corresponding to the pressure in the high-pressure pipe 8H is transmitted via the rear wheel side differential device 17. It is transmitted to the rear wheels 19 and shifts to a four wheel drive state.

In the first to fourth embodiments, the case where the rear wheel side differential device 17 is provided has been described, but the present invention is not limited to this, and the rear wheel differential device 17 is not limited thereto.
Is omitted, and instead of this, the left and right axles 18L and 18R of the left and right rear wheels 19L and 19R are individually provided with pump motors 10L and 1L.
0R may be provided. In this case, when different loads are applied to the left and right wheels during turning or the like, each pump motor 10L, 10R naturally causes a difference in discharge flow rate according to the difference. Therefore, the differential function equivalent to that of the differential device can be exhibited.

In each of the above-described embodiments, the case where the forward / reverse switching electromagnetic directional switching valve 9 is incorporated in the pump motor 10 has been described, but the present invention is not limited to this, and the pump motor 10 may be provided outside the pump motor 10. It may be provided separately. Further, in the above-mentioned actual form, the embodiment based on the front-wheel drive vehicle has been described, but the present invention is not limited to this, and when the rear-wheel drive vehicle is based, the piston pump 6 is arranged on the rear wheel side and the pump motor 10 is used. By arranging on the front wheel side, it is possible to obtain the same effects as those of the above-described embodiment.

Furthermore, in each of the above embodiments,
Has been described discharge flow rate characteristics of the piston pump 6 and the pump motor 10 is 2, the discharge flow rate characteristics of the swash plate type variable displacement pump motor 10, a predetermined wheel speed V ₁
Or kept constant flow rate stops increasing the discharge flow rate when it becomes equal to or greater than a predetermined wheel speed V ₁ is less than the wheel speed V
The increase of the discharge flow rate with respect to the increase of the wheel speed may be gradually changed from r.

[0058]

As described above, in the four-wheel drive vehicle according to the first aspect, the working fluid having a flow rate corresponding to the rotational speed is discharged from the fluid pressure pump by the rotation of the drive axle driven by the main motor. The working fluid is supplied to the fluid pressure pump motor of the fluid pressure driving means through the first flow path. Here, when the rotational speed difference between the drive axle and the driven axle is smaller than the reference rotational speed difference and the drive force is not transmitted from the drive axle to the driven axle as when traveling on a high friction coefficient road,
The control means controls the electromagnetic switching valve to switch to the first position. At this time, since the discharge port and the suction port of the fluid pressure pump are in communication with each other, the working fluid discharged from the discharge port of the fluid pressure pump does not flow into the first flow passage, but passes through the bypass flow passage and the electromagnetic switching valve. Flow toward the suction side of the fluid pressure pump. Therefore, the vibration due to the flow arterial movement of the hydraulic oil does not occur in the first flow path, so that it is possible to suppress noise and vibration to the floor in the vehicle. Further, since the working fluid does not flow in the first flow path extending as a long pipe in the lower portion of the floor, pressure loss due to pipe resistance or the like is reduced, and it is possible to prevent deterioration of fuel consumption and temperature rise of the working fluid.

In the four-wheel drive vehicle according to the second aspect of the present invention, when the rotational speed difference between the drive axle and the driven axle is smaller than the reference rotational speed difference and the drive force is not transmitted from the drive axle to the driven axle. When the control means controls the electromagnetic switching valve to switch to the first position, the discharge port and the suction port of the fluid pressure pump are brought into communication with each other, and the working fluid discharged from the discharge port of the fluid pressure pump has a high pressure flow path. Flow into the suction port side of the fluid pressure pump through the bypass flow path and the electromagnetic switching valve, so that the same effect as in claim 1 can be obtained. Further, for example, it is expected that the working fluid discharged from the fluid pressure pump will be confined in the high-pressure passage when the passage of the forward-reverse switching switching valve does not switch when the vehicle moves backward. Since the control fluid is switched to the first position by the control means, the working fluid in the high pressure passage flows to the suction port side of the fluid pressure pump, and the working fluid is not enclosed in the high pressure passage. No braking torque is generated and the driver does not feel uncomfortable.

Further, in the four-wheel drive vehicle according to the third aspect, when the driving force is not transmitted from the drive axle to the driven axle as in the case of traveling on a high friction coefficient road, the flow control valve has a control port. A low-pressure working fluid is input, and the flow control valve is switched to a first position that connects the input port and the output port via the throttle. At this time, since the working fluid flowing from the supply source to the fluid pressure pump through the throttle is restricted, the fluid pressure pump has a minimum discharge flow rate. Therefore, the working fluid discharged from the discharge port of the fluid pressure pump flows into the first flow path only at a small flow rate, and the vibration due to the flow arterial motion of the working oil does not occur in the first flow path. And vibration can be suppressed. In addition, pressure loss due to pipe resistance and the like can be reduced, and deterioration of fuel efficiency and temperature rise of the working fluid can be prevented.

Further, in the four-wheel drive vehicle according to the fourth aspect, the rotational speed difference between the drive axle and the driven axle is smaller than the reference rotational speed difference, such as when traveling on a high friction coefficient road, and the drive axle to the driven axle is moved. When the driving force is not transmitted, the control means controls the electromagnetic flow control valve to switch to the first position. At this time, since the working fluid flowing from the supply source to the fluid pressure pump through the throttle is restricted,
The fluid pressure pump has a minimum discharge flow rate. Therefore,
Since the working fluid discharged from the discharge port of the fluid pressure pump flows into the first flow path only at a small flow rate, it is possible to obtain the same effect as that of the third aspect.

Further, in the four-wheel drive vehicle according to the fifth aspect, when the drive force is not transmitted from the drive axle to the driven axle as when traveling on a high friction coefficient road, the fluid pressure supply means is used. The fluid pressure detecting means detects that the working fluid to be discharged has a low pressure. Based on the detection result of the fluid pressure detection means, the control means controls the electromagnetic flow control valve to switch to the first position. At this time, since the working fluid flowing from the supply source to the fluid pressure pump through the throttle is restricted, the fluid pressure pump has a minimum discharge flow rate.
Therefore, since the working fluid discharged from the discharge port of the fluid pressure pump flows into the first flow path only at a small flow rate, the same effect as in claim 3 can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing discharge flow rate characteristics of a fluid pressure pump and a fluid pressure pump motor according to the present invention.

FIG. 3 is a block diagram showing a control means according to the present invention.

FIG. 4 is a characteristic diagram showing a relationship between a front and rear axle speed difference and a transmission torque.

FIG. 5 is a schematic configuration diagram showing a second embodiment of the present invention.

FIG. 6 is a schematic configuration diagram showing a third embodiment of the present invention.

FIG. 7 is a schematic configuration diagram showing a fourth embodiment of the present invention.

[Explanation of symbols]

1 Engine (Main Motor) 4 Front Axle (Drive Axle) 6 Suction Throttling Piston Pump (Fluid Pressure Pump) 6b Suction Throttling Piston Pump Suction Port 6c Suction Throttling Piston Pump Discharge Port 8H High Pressure Piping (1st Flow Path) , High-pressure passage) 8L low-pressure pipe (second passage, low-pressure passage) 9 forward-reverse switching switching valve 10 swash plate type variable displacement pump motor (fluid pressure pump motor) 18 rear axle (driven axle) 20 communication pipe ( By-pass flow path) 22 Electromagnetic switching valve 24 Controller (control means) 26 Front axle rotation speed sensor (rotation speed difference detection means) 28 Rear axle rotation speed sensor (rotation speed difference detection means) 34 Flow control valve 34a Input port 34b Output port 34c Control port 34e Throttle 36 Electromagnetic flow control valve 36a Input port 36b Output port 36c Solenoid 36e Throttle 38 Pressure switch Ji (fluid pressure detection means) .DELTA.N _F standard rotational speed difference

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroo Kitada 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd.

Claims (5)

[Claims] 1. A drive axle driven by a prime mover,
A fluid pressure supply means having a fluid pressure pump that rotates in conjunction with the drive axle and discharges a working fluid; a fluid pressure drive means having a fluid pressure pump motor that rotates in conjunction with the driven axle; and the fluid pressure pump. Of the fluid pressure driving means, and a second flow path that communicates the discharge port of the fluid pressure driving means with the suction opening of the fluid pressure pump. In a four-wheel drive vehicle, a bypass flow passage that connects the discharge side and the suction side of the fluid pressure pump, and a communication state of the discharge port and the suction port of the fluid pressure pump that are inserted in the bypass flow passage. And a second position where the discharge port and the suction port of the fluid pressure pump are in a non-communication state, and a rotational speed difference that detects a rotational speed difference between the drive axle and the driven axle. Detection means and detection by the rotational speed difference detection means Control means for performing switching control of the solenoid operated directional control valve based on the difference in the number of revolutions, wherein the control means is based on a value where the difference in the number of revolutions of the drive axle and the driven axle generated in the two-wheel drive traveling state is small. The rotation speed difference is preset, and when the detected value of the rotation speed difference by the rotation speed difference detection means is equal to or less than the reference rotation speed difference, the electromagnetic switching valve is switched to the first position and the rotation speed difference A four-wheel drive vehicle, wherein the electromagnetic switching valve is switched to the second position when a detected value exceeds the reference rotational speed difference. 2. A drive axle driven by a prime mover,
A fluid pressure supply means having a fluid pressure pump that rotates in conjunction with the drive axle and discharges a working fluid, a fluid pressure pump motor that rotates in conjunction with the driven axle, and a fluid pressure pump motor disposed near the fluid pressure pump motor. A forward / reverse switching switching valve for switching the flow paths for the suction port and the discharge port of the fluid pressure pump motor, and a high-pressure flow path for communicating the discharge port of the fluid pressure pump with the suction port of the forward / reverse switching switch valve. A four-wheel drive vehicle including a low-pressure passage that communicates the suction port of the forward / reverse switching switching valve and the discharge port of the fluid pressure pump motor, wherein the discharge port side and the suction port side of the fluid pressure pump And a first position for inserting the bypass flow passage into communication with the discharge port and the pump suction port of the fluid pressure pump, and the discharge port and the pump suction port of the fluid pressure pump. To disconnect the An electromagnetic switching valve for switching between two positions, a rotational speed difference detecting means for detecting a rotational speed difference between the drive axle and the driven axle, and the electromagnetic switching based on the rotational speed difference detected by the rotational speed difference detecting means. A control means for controlling valve switching, wherein the control means presets a value having a small rotational speed difference between the drive axle and the driven axle generated in a two-wheel drive traveling state as a reference rotational speed difference, When the detected value of the rotational speed difference by the rotational speed difference detection means is less than or equal to the reference rotational speed difference, the electromagnetic switching valve is switched to the first position, and the detected value of the rotational speed difference exceeds the reference rotational speed difference. A four-wheel drive vehicle, wherein the electromagnetic switching valve is sometimes switched to the second position. 3. A drive axle driven by a prime mover,
A fluid pressure supply unit having a fluid pressure pump that rotates in association with the drive axle and discharges the working fluid sucked from a supply source of the working fluid, and a fluid pressure having a fluid pressure pump motor that rotates in association with the driven axle. A first means for communicating the driving means with the discharge port of the fluid pressure pump and the suction port of the fluid pressure driving means.
A four-wheel drive vehicle comprising: a flow path; and a second flow path that communicates the discharge port of the fluid pressure drive means with the suction port of the fluid pressure pump, wherein the supply source and the suction port of the fluid pressure pump are provided. An input port connected to the supply source side, an output port connected to the suction port side of the fluid pressure pump, and a part of the working fluid discharged from the discharge port of the fluid pressure pump in the suction flow path between Is inserted as a control pressure and a pilot operated type flow control valve having a throttle for limiting the flow of working fluid, and the flow control valve does not transmit the driving force to the driven axle. When a low-pressure working fluid is input as a control pressure to the control port, it is switched to a first position communicating the input port and the output port via the throttle, and the driving force is transmitted to the driven axle. Of a predetermined pressure Four-wheel drive vehicle, wherein said said input port and said output port that switched to the second position for communicating without via the aperture when the dynamic fluid is inputted to the control port as the control pressure. 4. A drive axle driven by a prime mover,
A fluid pressure supply unit having a fluid pressure pump that rotates in association with the drive axle and discharges the working fluid sucked from a supply source of the working fluid, and a fluid pressure having a fluid pressure pump motor that rotates in association with the driven axle. A first means for communicating the driving means with the discharge port of the fluid pressure pump and the suction port of the fluid pressure driving means.
A four-wheel drive vehicle comprising: a flow path; and a second flow path that communicates the discharge port of the fluid pressure drive means with the suction port of the fluid pressure pump, wherein the supply source and the suction port of the fluid pressure pump are provided. An input port connected to the supply source side by being inserted in the suction flow path between
An output port connected to the suction port side of the fluid pressure pump,
A first position having a restrictor for restricting the flow of the working fluid, and connecting the input port and the output port via the restrictor; and the input port and the output port without the restrictor. An electromagnetic flow control valve that switches to a second position that is in communication, a rotation speed difference detection means that detects a rotation speed difference between the drive axle and the driven axle, and a rotation speed difference detected by the rotation speed difference detection means. And a control means for performing switching control of the electromagnetic flow control valve, wherein the control means preliminarily sets a value having a small rotational speed difference between the drive axle and the driven axle generated in a two-wheel drive traveling state as a reference rotational speed difference. When the detected value of the rotational speed difference by the rotational speed difference detection means is equal to or less than the reference rotational speed difference, the electromagnetic flow control valve is switched to the first position, and the detected value of the rotational speed difference is Reference speed difference The four-wheel drive vehicle, characterized in that switching the electromagnetic flow control valve to said second position when exceeded. 5. A drive axle driven by a prime mover,
A fluid pressure supply unit having a fluid pressure pump that rotates in association with the drive axle and discharges the working fluid sucked from a supply source of the working fluid, and a fluid pressure having a fluid pressure pump motor that rotates in association with the driven axle. A first means for communicating the driving means with the discharge port of the fluid pressure pump and the suction port of the fluid pressure driving means.
A four-wheel drive vehicle comprising: a flow path; and a second flow path that communicates the discharge port of the fluid pressure drive means with the suction port of the fluid pressure pump, wherein the supply source and the suction port of the fluid pressure pump are provided. An input port connected to the supply source side by being inserted in a suction flow path between the output port and an output port connected to the suction port side of the fluid pressure pump, and a throttle for restricting the flow of the working fluid, and A first connecting the input port and the output port via a diaphragm
An electromagnetic flow control valve that switches between a position and a second position that communicates the input port and the output port without passing through the throttle; and a change state of the pressure of the working fluid discharged from the fluid pressure supply means. A fluid pressure detecting means for detecting, and a control means for performing switching control of the electromagnetic flow control valve based on a detection result of the fluid pressure detecting means, wherein the control means controls the driven axle by the fluid pressure detecting means. On the other hand, when it is detected that a low-pressure working fluid that does not transmit the driving force is reached, the electromagnetic flow control valve is switched to the first position, and the fluid pressure detecting means causes the driving force to be applied to the driven axle. The four-wheel drive vehicle is characterized in that the electromagnetic flow control valve is switched to the second position when it is detected that the working fluid having a predetermined pressure for transmitting is transmitted.